If you find yourself sardined in the morning subway, imagine what it will be like in 2050, when three-quarters of the planet’s population will be living in urban areas. Or better yet, see what a select group of artists and architects — such as Zaha Hadid and Francis Alys — have already envisioned in Global Cities at London’s Tate Modern. The new exhibit, which runs through August 27, explores the shifting identities of 10 of the world’s mega-cities, including Tokyo, Sao Paolo, Mumbai and Istanbul. Through a series of real and imaginary visions, you’ll learn how the globe’s mushrooming metropolises are fast impacting our quality of life (one out of three people, for example, already live in slums). Plus you’ll also get to see a novel interpretation of London — as blocks made of biscuits and a tower resting on a shoe.